SMART ARM-based Microcontrollers
AT10732: SAM L True Random Number Generator
(TRNG) Driver
APPLICATION NOTE
Introduction
®
®
This driver for Atmel | SMART ARM -based microcontrollers provides an
interface for the configuration and management of the device's True Random
Number Generator functionality.
The following driver API modes are covered by this manual:
•
Polled APIs
•
Callback APIs
The following peripheral is used by this module:
•
TRNG (True Random Number Generator)
The following devices can use this module:
•
Atmel | SMART SAM L21/L22
The outline of this documentation is as follows:
•
Prerequisites
•
Module Overview
•
Special Considerations
•
Extra Information
•
Examples
•
API Overview
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Table of Contents
Introduction......................................................................................................................1
1. Software License....................................................................................................... 3
2. Prerequisites..............................................................................................................4
3. Module Overview....................................................................................................... 5
4. Special Considerations.............................................................................................. 6
5. Extra Information....................................................................................................... 7
6. Examples................................................................................................................... 8
7. API Overview............................................................................................................. 9
7.1.
7.2.
7.3.
7.4.
Variable and Type Definitions....................................................................................................... 9
7.1.1.
Type trng_callback_t......................................................................................................9
7.1.2.
Variable _trng_instance................................................................................................. 9
Structure Definitions..................................................................................................................... 9
7.2.1.
Struct trng_config...........................................................................................................9
7.2.2.
Struct trng_events..........................................................................................................9
7.2.3.
Struct trng_module........................................................................................................ 9
Function Definitions....................................................................................................................10
7.3.1.
Driver Initialization and Configuration.......................................................................... 10
7.3.2.
Read TRNG Result......................................................................................................12
7.3.3.
Callback Management................................................................................................. 12
7.3.4.
Job Management......................................................................................................... 14
Enumeration Definitions............................................................................................................. 15
7.4.1.
Enum trng_callback..................................................................................................... 15
7.4.2.
Enum trng_job_type.....................................................................................................15
8. Extra Information for TRNG Driver.......................................................................... 16
8.1.
8.2.
8.3.
8.4.
Acronyms....................................................................................................................................16
Dependencies.............................................................................................................................16
Errata..........................................................................................................................................16
Module History............................................................................................................................16
9. Examples for TRNG Driver...................................................................................... 17
9.1.
9.2.
Quick Start Guide for TRNG - Basic...........................................................................................17
9.1.1.
Setup........................................................................................................................... 17
9.1.2.
Implementation............................................................................................................ 18
Quick Start Guide for TRNG - Callback......................................................................................18
9.2.1.
Setup........................................................................................................................... 19
9.2.2.
Implementation............................................................................................................ 21
10. Document Revision History..................................................................................... 22
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1.
Software License
Redistribution and use in source and binary forms, with or without modification, are permitted provided
that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
following disclaimer in the documentation and/or other materials provided with the distribution.
3. The name of Atmel may not be used to endorse or promote products derived from this software without
specific prior written permission.
4. This software may only be redistributed and used in connection with an Atmel microcontroller product.
THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE EXPRESSLY AND SPECIFICALLY
DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
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2.
Prerequisites
There are no prerequisites for this module.
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3.
Module Overview
This driver provides an interface for the TRNG functions on the device.
As soon as the TRNG is enabled, the module provides a new 32-bit random data, for every 84
CLK_TRNG_APB clock cycles.
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4.
Special Considerations
There are no special considerations for this module.
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5.
Extra Information
For extra information, see Extra Information for TRNG Driver. This includes:
•
Acronyms
•
Dependencies
•
Errata
•
Module History
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6.
Examples
For a list of examples related to this driver, see Examples for TRNG Driver.
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7.
API Overview
7.1.
Variable and Type Definitions
7.1.1.
Type trng_callback_t
typedef void(* trng_callback_t )(struct trng_module *const module_inst)
Type definition for a TRNG module callback function.
7.1.2.
Variable _trng_instance
struct trng_module * _trng_instance
7.2.
Structure Definitions
7.2.1.
Struct trng_config
Configuration structure for a True Random Number Generator.
Table 7-1. Members
Type Name
bool
7.2.2.
Description
run_in_standby If true, the True Random Number Generator will not be stopped in standby
sleep mode
Struct trng_events
Event flags for the TRNG module. This is used to enable and disable events via trng_enable_events()
and trng_disable_events().
Table 7-2. Members
7.2.3.
Type
Name
Description
bool
generate_event_on_data_ready
Enable event generation on random data ready
Struct trng_module
TRNG software instance structure, used to retain software state information of an associated hardware
module instance.
Note: The fields of this structure should not be altered by the user application; they are reserved for
module-internal use only.
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7.3.
Function Definitions
7.3.1.
Driver Initialization and Configuration
7.3.1.1.
Function trng_init()
Initializes a hardware TRNG module instance.
enum status_code trng_init(
struct trng_module *const module_inst,
Trng *const hw,
struct trng_config *const config)
Enables the clock and initializes the TRNG module, based on the given configuration values.
Table 7-3. Parameters
Data direction
Parameter name
Description
[in, out]
module_inst
Pointer to the software module instance struct
[in]
hw
Pointer to the TRNG hardware module
[in]
config
Pointer to the TRNG configuration options struct
Returns
Status of the initialization procedure.
Table 7-4. Return Values
7.3.1.2.
Return value
Description
STATUS_OK
The module was initialized successfully
Function trng_get_config_defaults()
Initializes all members of a TRNG configuration structure to safe defaults.
void trng_get_config_defaults(
struct trng_config *const config)
Initializes all members of a given True Random Number Generator configuration structure to safe known
default values. This function should be called on all new instances of these configuration structures
before being modified by the user application.
The default configuration is as follows:
•
True Random Number Generator will not be stopped in standby sleep mode
Table 7-5. Parameters
Data direction
Parameter name
Description
[out]
config
Configuration structure to initialize to default values
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7.3.1.3.
Function trng_enable()
Enables a TRNG that was previously configured.
void trng_enable(
struct trng_module *const module_inst)
Enables True Random Number Generator that was previously configured via a call to trng_init().
Table 7-6. Parameters
Data direction Parameter name Description
[in]
7.3.1.4.
module_inst
Software instance for the True Random Number Generator
peripheral
Function trng_disable()
Disables a TRNG that was previously enabled.
void trng_disable(
struct trng_module *const module_inst)
Disables True Random Number Generator that was previously started via a call to trng_enable().
Table 7-7. Parameters
Data direction Parameter name Description
[in]
7.3.1.5.
module_inst
Software instance for the True Random Number Generator
peripheral
Function trng_enable_events()
Enables a TRNG event output.
void trng_enable_events(
struct trng_module *const module_inst,
struct trng_events *const events)
Enables output events from the True Random Number Generator module. See Section Struct trng_events
for a list of events this module supports.
Note: Events cannot be altered while the module is enabled.
Table 7-8. Parameters
7.3.1.6.
Data direction
Parameter name
Description
[in]
module_inst
Software instance for the TRNG peripheral
[in]
events
Struct containing flags of events to enable
Function trng_disable_events()
Disables a TRNG event output.
void trng_disable_events(
struct trng_module *const module_inst,
struct trng_events *const events)
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Disables output events from the True Random Number Generator module. See Section Struct
trng_events for a list of events this module supports.
Note: Events cannot be altered while the module is enabled.
Table 7-9. Parameters
Data direction
Parameter name
Description
[in]
module_inst
Software instance for the TRNG peripheral
[in]
events
Struct containing flags of events to disable
7.3.2.
Read TRNG Result
7.3.2.1.
Function trng_read()
Read the random data result.
enum status_code trng_read(
struct trng_module *const module_inst,
uint32_t * result)
Reads the random data result.
Table 7-10. Parameters
Data direction
Parameter name
Description
[in]
module_inst
Pointer to the TRNG software instance struct
[out]
result
Pointer to store the result value in
Returns
Status of the TRNG read request.
Table 7-11. Return Values
Return value
Description
STATUS_OK
The result was retrieved successfully
STATUS_BUSY
A random result was not ready
7.3.3.
Callback Management
7.3.3.1.
Function trng_register_callback()
Registers a callback.
enum status_code trng_register_callback(
struct trng_module *const module,
trng_callback_t callback_func,
enum trng_callback callback_type)
Registers a callback function which is implemented by the user.
Note: The callback must be enabled by trng_enable_callback, in order for the interrupt handler to call it
when the conditions for the callback type is met.
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Table 7-12. Parameters
Data direction
Parameter name
Description
[in]
module
Pointer to TC software instance struct
[in]
callback_func
Pointer to callback function
[in]
callback_type
Callback type given by an enum
Table 7-13. Return Values
7.3.3.2.
Return value
Description
STATUS_OK
The function exited successfully
Function trng_unregister_callback()
Unregisters a callback.
enum status_code trng_unregister_callback(
struct trng_module * module,
enum trng_callback callback_type)
Unregisters a callback function implemented by the user. The callback should be disabled before it is
unregistered.
Table 7-14. Parameters
Data direction
Parameter name
Description
[in]
module
Pointer to TC software instance struct
[in]
callback_type
Callback type given by an enum
Table 7-15. Return Values
7.3.3.3.
Return value
Description
STATUS_OK
The function exited successfully
Function trng_enable_callback()
Enables callback.
void trng_enable_callback(
struct trng_module *const module,
enum trng_callback callback_type)
Enables the callback function registered by trng_register_callback. The callback function will be called
from the interrupt handler when the conditions for the callback type are met.
Table 7-16. Parameters
Data direction
Parameter name
Description
[in]
module
Pointer to TRNG software instance struct
[in]
callback_type
Callback type given by an enum
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7.3.3.4.
Function trng_disable_callback()
Disables callback.
void trng_disable_callback(
struct trng_module *const module,
enum trng_callback callback_type)
Disables the callback function registered by the trng_register_callback.
Table 7-17. Parameters
Data direction
Parameter name
Description
[in]
module
Pointer to TRNG software instance struct
[in]
callback_type
Callback type given by an enum
7.3.4.
Job Management
7.3.4.1.
Function trng_read_buffer_job()
Read multiple random data from TRNG.
enum status_code trng_read_buffer_job(
struct trng_module *const module_inst,
uint32_t * buffer,
uint32_t number)
As soon as the TRNG is enabled, the module provides a new 32-bits random data for every 84
CLK_TRNG_APB clock cycles.
Table 7-18. Parameters
Data direction
Parameter name
Description
[in]
module_inst
Pointer to the TRNG software instance struct
[in]
number
Number of random data to get
[out]
buffer
Buffer to store the random data
Returns
Status of the job start.
Table 7-19. Return Values
7.3.4.2.
Return value
Description
STATUS_OK
The read job was started successfully and is in progress
STATUS_BUSY
The TRNG is already busy with another job
Function trng_get_job_status()
Gets the status of a job.
enum status_code trng_get_job_status(
struct trng_module * module_inst,
enum trng_job_type type)
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Gets the status of an ongoing or the last job.
Table 7-20. Parameters
Data direction
Parameter name
Description
[in]
module_inst
Pointer to the TRNG software instance struct
[in]
type
Type of job to abort
Returns
Status of the job.
7.3.4.3.
Function trng_abort_job()
Aborts an ongoing job.
void trng_abort_job(
struct trng_module * module_inst,
enum trng_job_type type)
Table 7-21. Parameters
Data direction
Parameter name
Description
[in]
module_inst
Pointer to the TRNG software instance struct
[in]
type
Type of job to abort
7.4.
Enumeration Definitions
7.4.1.
Enum trng_callback
Enum for possible callback types for the TRNG module.
Table 7-22. Members
7.4.2.
Enum value
Description
TRNG_CALLBACK_READ_BUFFER
Callback for specific number of random data ready
Enum trng_job_type
Enum for the possible types of TRNG asynchronous jobs that may be issued to the driver.
Table 7-23. Members
Enum value
Description
TRNG_JOB_READ_BUFFER
Asynchronous TRNG read into a user provided buffer
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8.
Extra Information for TRNG Driver
8.1.
Acronyms
8.2.
Acronym
Description
TRNG
True Random Number Generator
Dependencies
This driver has no dependencies.
8.3.
Errata
There are no errata related to this driver.
8.4.
Module History
An overview of the module history is presented in the table below, with details on the enhancements and
fixes made to the module since its first release. The current version of this corresponds to the newest
version in the table.
Changelog
Initial Release
Atmel AT10732: SAM L True Random Number Generator (TRNG) Driver [APPLICATION NOTE]
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9.
Examples for TRNG Driver
This is a list of the available Quick Start guides (QSGs) and example applications for SAM True Random
Number Generator (TRNG) Driver. QSGs are simple examples with step-by-step instructions to configure
and use this driver in a selection of use cases. Note that QSGs can be compiled as a standalone
application or be added to the user application.
•
•
9.1.
Quick Start Guide for TRNG - Basic
Quick Start Guide for TRNG - Callback
Quick Start Guide for TRNG - Basic
In this use case, the True Random Number Generator (TRNG) module is configured for:
•
The TRNG peripheral will not be stopped in standby sleep mode
This use case will read random data in polling mode repeatedly. After reading a data, the board LED will
be toggled.
9.1.1.
Setup
9.1.1.1.
Prerequisites
There are no special setup requirements for this use-case.
9.1.1.2.
Code
Copy-paste the following setup code to your user application:
/* TRNG module software instance (must not go out of scope while in use) */
static struct trng_module trng_instance;
void configure_trng(void)
{
/* Create a new configuration structure for the TRNG settings
* and fill with the default module settings. */
struct trng_config config_trng;
trng_get_config_defaults(&config_trng);
/* Alter any TRNG configuration settings here if required */
/* Initialize TRNG with the user settings */
}
trng_init(&trng_instance, TRNG, &config_trng);
Add to user application initialization (typically the start of main()):
system_init();
configure_trng();
trng_enable(&trng_instance);
9.1.1.3.
Workflow
1.
Create a TRNG device instance struct, which will be associated with a TRNG peripheral hardware
instance.
static struct trng_module trng_instance;
Note: Device instance structures shall never go out of scope when in use.
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2.
Create a new function configure_trng(), which will be used to configure the overall TRNG
peripheral.
void configure_trng(void)
3.
Create a TRNG peripheral configuration structure that will be filled out to set the module
configuration.
struct trng_config config_trng;
4.
Fill the TRNG peripheral configuration structure with the default module configuration values.
trng_get_config_defaults(&config_trng);
5.
Initialize the TRNG peripheral and associate it with the software instance structure that was defined
previously.
trng_init(&trng_instance, TRNG, &config_trng);
6.
Enable the now initialized TRNG peripheral.
trng_enable(&trng_instance);
9.1.2.
Implementation
9.1.2.1.
Code
Copy-paste the following code to your user application:
uint32_t random_result;
while (true) {
while (trng_read(&trng_instance, &random_result) != STATUS_OK) {
}
port_pin_toggle_output_level(LED_0_PIN);
/* Add a short delay to see LED toggle */
volatile uint32_t delay = 50000;
while(delay--) {
}
9.1.2.2.
}
Workflow
1.
Make the application loop infinitely.
while (true) {
2.
Start to read a random data from TRNG until success.
while (trng_read(&trng_instance, &random_result) != STATUS_OK) {
}
3.
Toggle the board LED to indicate a random data is read.
port_pin_toggle_output_level(LED_0_PIN);
/* Add a short delay to see LED toggle */
volatile uint32_t delay = 50000;
while(delay--) {
}
9.2.
Quick Start Guide for TRNG - Callback
In this use case, the True Random Number Generator (TRNG) module is configured for:
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•
The TRNG peripheral will not be stopped in standby sleep mode
This use case will read random data in interrupt mode repeatly. After reading specific size of buffer data,
the board LED will be toggled.
9.2.1.
Setup
9.2.1.1.
Prerequisites
There are no special setup requirements for this use-case.
9.2.1.2.
Code
Copy-paste the following setup code to your user application:
bool volatile trng_read_done = false;
void configure_trng(void);
void configure_trng_callback(void);
void trng_complete_callback(struct trng_module *const module_inst);
/* TRNG module software instance (must not go out of scope while in use) */
static struct trng_module trng_instance;
void configure_trng(void)
{
/* Create a new configuration structure for the TRNG settings
* and fill with the default module settings. */
struct trng_config config_trng;
trng_get_config_defaults(&config_trng);
/* Alter any TRNG configuration settings here if required */
/* Initialize TRNG with the user settings */
}
trng_init(&trng_instance, TRNG, &config_trng);
void trng_complete_callback(struct trng_module *const module_inst)
{
}
trng_read_done = true;
void configure_trng_callback(void)
{
}
trng_register_callback(&trng_instance, trng_complete_callback,
TRNG_CALLBACK_READ_BUFFER);
trng_enable_callback(&trng_instance, TRNG_CALLBACK_READ_BUFFER);
Add to user application initialization (typically the start of main()):
system_init();
configure_trng();
configure_trng_callback();
trng_enable(&trng_instance);
9.2.1.3.
Workflow
1.
Create a TRNG device instance struct, which will be associated with a TRNG peripheral hardware
instance.
static struct trng_module trng_instance;
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2.
Note: Device instance structures shall never go out of scope when in use.
Create a new function configure_trng(), which will be used to configure the overall TRNG
peripheral.
void configure_trng(void)
3.
Create a TRNG peripheral configuration structure that will be filled out to set the module
configuration.
struct trng_config config_trng;
4.
Fill the TRNG peripheral configuration structure with the default module configuration values.
trng_get_config_defaults(&config_trng);
5.
Initialize the TRNG peripheral and associate it with the software instance structure that was defined
previously.
trng_init(&trng_instance, TRNG, &config_trng);
6.
Create a new callback function.
void trng_complete_callback(struct trng_module *const module_inst)
{
}
7.
trng_read_done = true;
Create a callback status software flag.
bool volatile trng_read_done = false;
8.
Let the callback function set the flag to true when read job done.
trng_read_done = true;
9.
Create a new function configure_trng_callback(), which will be used to configure the
callbacks.
void configure_trng_callback(void)
{
}
trng_register_callback(&trng_instance, trng_complete_callback,
TRNG_CALLBACK_READ_BUFFER);
trng_enable_callback(&trng_instance, TRNG_CALLBACK_READ_BUFFER);
10. Register callback function.
trng_register_callback(&trng_instance, trng_complete_callback,
TRNG_CALLBACK_READ_BUFFER);
11. Enable the callbacks.
trng_enable_callback(&trng_instance, TRNG_CALLBACK_READ_BUFFER);
12. Enable the now initialized TRNG peripheral.
trng_enable(&trng_instance);
Note: This should not be done until after the TRNG is set up and ready to be used.
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9.2.2.
Implementation
9.2.2.1.
Code
Copy-paste the following code to your user application:
uint32_t random_buffer[5];
while (true) {
trng_read_buffer_job(&trng_instance, random_buffer, 5);
while (!trng_read_done) {
}
trng_read_done = false;
port_pin_toggle_output_level(LED_0_PIN);
/* Add a short delay to see LED toggle */
volatile uint32_t delay = 50000;
while(delay--) {
}
9.2.2.2.
}
Workflow
1.
Make the application loop infinitely.
while (true) {
2.
Start an asynchronous TRNG read job, to store random data into the global buffer and generate a
callback when complete.
trng_read_buffer_job(&trng_instance, random_buffer, 5);
3.
Wait until the asynchronous read job is complete.
while (!trng_read_done) {
}
trng_read_done = false;
4.
Toggle the board LED to indicate specific size of random data were read.
port_pin_toggle_output_level(LED_0_PIN);
/* Add a short delay to see LED toggle */
volatile uint32_t delay = 50000;
while(delay--) {
}
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10.
Document Revision History
Doc. Rev.
Date
Comments
42444B
01/2016
Added support for SAM L22
42444A
06/2015
Initial document release
Atmel AT10732: SAM L True Random Number Generator (TRNG) Driver [APPLICATION NOTE]
Atmel-42444B-SAM-True-Random-Number-Generator-TRNG-Driver_AT10732_Application Note-01/2016
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2016 Atmel Corporation. / Rev.: Atmel-42444B-SAM-True-Random-Number-Generator-TRNG-Driver_AT10732_Application Note-01/2016
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